Socioeconomic disadvantage is associated with psychosocial and physical environments that reduce sleep duration and sleep quality. The cumulative effects of these differences in sleep may contribute to social disparities in critical developmental trajectories for children and adolescents. The proposed research will investigate the biopsychosocial determinants of adolescent sleep, and the extent to which differential sleep trajectories during childhood contribute to differences in obesity and depression using the Fragile Families Study (FFS). As an ancillary study to the FFS age 15 wave, this application provides a rare opportunity to study sleep patterns in a well-characterized national cohort of primarily at-risk adolescents followed since birth. In Aim 1, we seek to estimate the long-term associations of early sleep-related behaviors with adolescent sleep. We hypothesize that the regular use of age-appropriate bedtimes with consistent bedtime routines during childhood is associated with adequate sleep duration for developmental age and better sleep quality among adolescents. In Aim 2, we will identify the relative importance of a range of biopsychosocial determinants of adolescent sleep, including school, community, family, and genetic factors. While sleep and circadian gene variants have shown associations with sleep patterns in adults, no research to date has investigated the genetics of adolescent sleep. In Aim 3, we estimate how trajectories of insufficient and low-quality sleep predict biological and psychological outcomes in adolescence. We hypothesize that children with shorter sleep duration and lower quality sleep are more likely to obese and report depression/depressive symptoms. Aim 4 investigates the direct and indirect effects of physical activity and screen time exposure on adolescent sleep, obesity, and depression. To achieve these aims, first we will add sleep-related questions to the multidimensional interview of the entire FFS adolescent sample (n~3,600). These questions address sleep duration, sleep timing, sleep quality, bedtime behaviors (e.g., technology at bedtime), and school start times. Second, we will collect one week of wrist and hip actigraphic data on 1,000 adolescent participants in order to directly monitor sleep timing, duration, and quality in addition to physical activity. During this same week, participants will provide a one-week multimedia exposure diary. Third, we will genotype the previously collected saliva samples (n~2800) for sleep and circadian candidate genes. These sources of additional sleep, physical activity, and screen time exposure information will be merged with the rich data collection efforts from FFS, which will be one of the longest-running population-based studies of health and development of children born in the US. This application will integrate multidisciplinary research into the most thorough actigraphy-based investigation to date of the social and ecological determinants of child and adolescent sleep patterns and further a novel approach for understanding social disparities in health.